Combined Use of Electroencephalography and Transcranial Electrical Stimulation: A Systematic Review

Area of Science:

• Neuroscience
• Neurotechnology
• Brain Stimulation

Background:

• Electroencephalography (EEG) and transcranial electrical stimulation (tES) are increasingly used together.
• Understanding their combined application is crucial for advancing brain modulation techniques.

Purpose of the Study:

• To systematically review the combined use of EEG and tES.
• To evaluate EEG's role in guiding, monitoring, and assessing tES interventions.
• To assess the generalizability of EEG responses across different tES protocols.

Main Methods:

• A comprehensive literature search was conducted across major scientific databases.
• 162 studies were identified using keywords related to EEG and various tES modalities.
• Study quality was assessed using the Quality Assessment Tool for Quantitative Studies (QATQS).

Main Results:

• Most studies utilized post-stimulation EEG to evaluate neuromodulatory effects.
• Fewer studies employed real-time EEG for adaptive stimulation or protocol design.
• Significant heterogeneity in tES parameters and EEG metrics hindered reproducibility, with many reporting non-significant EEG changes.

Conclusions:

• EEG-informed, personalized tES protocols hold significant potential for clinical and research applications.
• The current research landscape shows limited use of real-time closed-loop systems.
• Methodological quality is generally low, and the connection between EEG changes and clinical outcomes requires further investigation.